Can I render an Alpha pass for an object in a scene?
I want to be able to place an object in a scene in front of a live actor. Is there a way to create a render pass that is embedded with an alpha channel for a specific object in the scene?
Thanks in advance.

Comments
Make sure you have no modelled scene, and that Draw Dome is off in render Settings, and that you have no backdrop in the Environment pane. Then save you render as .tiff or .png.
_if you save as PNG , then it has a transparent background _ _and TIF has an alpha channel